Chronic central nervous system effects of acute organophosphate pesticide intoxication. The Pesticide Health Effects Study Group.

Acute organophosphate pesticide poisonings cause substantial morbidity and mortality world wide; however, whether organophosphates cause chronic neurological sequelae has not been established. To see whether single episodes of acute unintentional organophosphate intoxication lead to chronic neuropsychological dysfunction, we carried out a retrospective study of agricultural workers in Nicaragua who had been admitted to hospital between July 1, 1986, and July 31, 1988, for occupationally related organophosphate intoxication. This "poisoned" group (36 men) was tested on average about two years after the episode of pesticide poisoning and compared with a matched control group. The poisoned group did much worse than the control group on all neuropsychological subtests, with significantly worse performance on five of six subtests of a World Health Organisation neuropsychological test battery and on 3 of 6 additional tests that assessed verbal and visual attention, visual memory, visuomotor speed, sequencing and problem solving, and motor steadiness and dexterity. Differences in neuropsychological performance could not be explained by other factors. The findings of a persistent decrease in neuropsychological performance among individuals with previous intoxication emphasise the importance of prevention of even single episodes of organophosphate poisoning.